This invention relates to a large-capacity flexible disk and a high-density type disk drive capable of accessing a large-capacity flexible disk and, in particular, to a high-density type disk drive capable of discriminating a large-capacity flexible disk from other flexible disks.
As well known, a flexible disk drive is a device for recording and reproducing data to and from flexible disks. As also well known, there are various flexible disks having different storage capacities. In the following description, those flexible disks having storage capacities of 1 Mbyte, 2 Mbyte, and 4 Mbyte will collectively be called small-capacity flexible disks while those flexible disks having storage capacities of 10 Mbyte and 21 Mbyte will collectively be called medium-capacity flexible disks.
In recent years, flexible disks have been improved to have much greater capacities. In comparison with the small-capacity and the medium-capacity flexible disks mentioned above, those flexible disks (hereinafter collectively called large-capacity flexible disks) having storage capacities of 128 Mbyte, 256 Mbyte, and 512 Mbyte, . . . are being developed.
In the following, a flexible disk drive capable of recording and reproducing data to and from the large-capacity flexible disks alone will be called a dedicated high-density flexible disk drive. A flexible disk drive capable of recording and reproducing data to and from the medium-capacity flexible disks alone will be called a dedicated medium-density flexible disk drive. A flexible disk drive capable of recording and reproducing data to and from the small-capacity flexible disks alone will be called a dedicated low-density flexible disk drive. Furthermore, a flexible disk drive capable of recording and reproducing data to and from all of the large-capacity, the medium-capacity, and the small-capacity flexible disks will be called a universal multi-density flexible disk drive. In addition, the dedicated high-density flexible disk drive and the universal multi-density flexible disk drive will collectively called a high-density type flexible disk drive.
One of the differences in mechanism between the dedicated low-density flexible disk drive and the high-density type flexible disk drive resides in the structure of a driving means for moving a carriage holding a magnetic head in a predetermined radial direction with respect to a flexible disk inserted in the drive. Specifically, the dedicated low-density flexible disk drive uses a stepping motor as the driving means while the high-density type flexible disk drive uses a linear motor, such as a voice coil motor (VCM), as the driving means.
Next, description will be made in more detail about the voice coil motor used as the driving means of the high-density type flexible disk drive. The voice coil motor comprises a voice coil located on opposite sides of a rear portion of the carriage and wound around a drive shaft parallel to the predetermined radial direction, and a magnetic circuit for producing a magnetic field intersecting an electric current flowing through the voice coil. With this structure, by flowing the electric current through the voice coil in a direction intersecting the magnetic field produced by the magnetic circuit, driving force is produced in an extending direction of the drive shaft as a result of interaction between the electric current and the magnetic field. Due to the driving force, the voice coil motor moves the carriage in the predetermined radial direction.
Conventional large-capacity flexible disks are identical in external shape with the small-capacity and the medium-capacity flexible disks. For all of these types, 3.5-inch disks have a flat rectangular shape having a width, a length, and a thickness of 90 mm, 94 mm, and 3.3 mm, respectively.
As well known, the small-capacity flexible disks are classified into three types having storage capacities of 1 Mbyte, 2 Mbyte, and 4 Mbyte, respectively. For convenience of description, the small-capacity flexible disks having storage capacities of 1 Mbyte, 2 Mbyte, and 4 Mbyte are called small-capacity (1M) flexible disks, small-capacity (2M) flexible disks, and small-capacity (4M) flexible disks, respectively.
In the dedicated low-density flexible disk drive, it is required to identify the storage capacity of 1 Mbyte, 2 Mbyte, and 4 Mbyte small-capacity flexible disks inserted therein. For this purpose, a case of each of the small-capacity flexible disks of 2 Mbyte and 4 Mbyte is provided with a 2-Mbyte identifier hole or the like to discriminate between the small-capacity flexible disks of 1 Mbyte and the small-capacity flexible disks of both 2 Mbyte and 4 Mbyte.
Besides, there are a wide variety of flexible disks having different storage capacities. Accordingly, the flexible disk drives must identify the type of the flexible disk inserted therein. To this end, each conventional flexible disk is provided in a plane of the case with an identifier hole corresponding to the type. As the identifier hole, it is known to form various identifier holes, such as a 2-Mbyte identifier hole and a 4-Mbyte identifier hole, in the plane of the case. Identification is carried out with reference to the presence or absence of the identifier hole. With so many disks in use, however, identification of a large number of types of the flexible disks is approaching a limit. This is because, in order to form or perforate the identifier hole, an unperforated area is required around the identifier hole. As a result, a wide area is required.